Final answer:
The option that is not one of the disadvantages of peer-to-peer networks is 'd. They centralize user account logins.'
Step-by-step explanation:
The option that is not one of the disadvantages of peer-to-peer networks is d. They centralize user account logins. Peer-to-peer networks actually distribute the responsibility of user account logins among the different devices on the network, which provides a more decentralized approach. This can be advantageous in terms of security and scalability.